12ax7's inside poweramp

[Misanthrope189]

Hey there,
I have a question about the 12ax7's inside the power amp I have. Should I ever change them? And if I get different tubes that are a different brand, should I go ahead and change the 12ax7's inside the power amp to the same brand as the new tubes I get, say if it's an upgrade to a better brand? I don't know how much the 12ax7's inside the power amp play a role in the overall tone.

Thanks a lot,
Nick

[DonP]

Power tubes have little gain, and a Class AB power amp require a split phase signal (one phase to do the push, one phase to drive the pull).

The 12AX7 gives gain and provides the roll of a phase splitter.

If you are really anal, get a 12AX7 that has matched side (a 12AX7 is like 2 tubes in one - you want each half to match). Otherwise, if your amp has a negative feeedback loop like most do, most any decent tube will work.

Should you ever change it? Only if something is wrong- i.e. don't fix it if it ain't broke.